Recently, display devices such as liquid crystal display devices, typified by, for example, a liquid crystal display television and a liquid crystal display monitor, have adopted a backlight as a light-emitting device for emitting light from the back, side or the like of a display panel. As the backlight, there is what is called a direct-lighting type in which a light source is disposed on a plane surface beneath the liquid crystal panel (a rear surface), for example. In addition, what is called an edge-lighting type exists in which a light source is disposed on two or one side of a light guide plate made of a transparent resin so that light incident on the light guide plate is reflected by a reflector disposed on the back surface of the light guide plate, and illuminates, for example, the surface of a liquid crystal display panel. Here, the direct-lighting type has an advantage of securing high brightness, but has a disadvantage of difficulty in achieving a thinner backlight. On the other hand, the edge-lighting type has an advantage of achieving a thinner backlight than the direct-lighting type, but has a disadvantage of difficulty in obtaining uniformity in the luminance for a large display.
A fluorescent tube such as a hot-cathode fluorescent tube or a cold-cathode fluorescent tube is widely used as the above-mentioned backlight device. On the other hand, technologies of backlight devices using light-emitting diodes (LEDs), which are one type of solid-state light-emitting elements, as a light source, have been recently developed as a substitute for the backlight devices using the fluorescent tubes.
Here, the backlight device is generally provided with a reflection plate (a reflector) configured to reflect light emitted from, for example, the LED toward, for example, an observer.
The related art disclosed in a Patent Official Gazette includes a technique that involves: the provision of a light guide plate having a light exit surface, a reflecting surface and a light entrance surface; the provision of a bottom plate and a sidewall under the light guide plate; the disposition of plural light-emitting diodes on the bottom plate; and the use of the sidewall as the reflecting surface (see Patent Document 1, for example). This Patent Document discloses that a film, sheet or the like made of resin such as white PET (polyethyleneterephthalate) or formed by a plating deposition of metal such as silver or aluminum is used, giving a specular reflection or high-reflectivity function to the sidewall in order to reflect light emitted from the light-emitting diodes.
Also, another Patent Official Gazette discloses a light emitting device provided with a reflector adapted to direct light toward the top face of an optical component in order to improve light extraction efficiency (see Patent Document 2, for example).
Patent Document 1: Japanese Patent Application Laid Open Publication No. 2005-108675
Patent Document 2: Japanese Patent Application Laid Open Publication No. 2005-57266